[xXx_Mr.Simpatia_xXx]

Code:

GetPlayerIDFromIP(ip[])
{
    new IP[16], playerid;
	for(new i = 0; i < MAX_PLAYERS; i++)
	{
	    if(IsPlayerConnected(i))
		{
		    GetPlayerIp(i, IP, sizeof(IP));
			if(strcmp(ip, IP, true)==0) return i = playerid;
        }
        else return INVALID_PLAYER_ID;
	}
	return playerid;
}

It can be used with the callback "OnRconLoginAttempt"

Code:

public OnRconLoginAttempt(ip[], password[], success)
{
    new nome[24], str[100], playerid;
    if(!success)
    {
        playerid = GetPlayerIDFromIP(ip);
        GetPlayerName(playerid, nome, sizeof(nome));
        format(str, 100, "%s has entered a wrong password", nome);
        SendClientMessageToAll(COLOR_WHITE, str);
    }
    return 1;
}

Sorry for my bad english :P